Active antenna system

ABSTRACT

The present invention relates to an active antenna system, AAS, for controlling coverage in a telecommunication network, and the AAS comprising a plurality of subarrays each having multiple radiating elements. The AAS is configured to provide coverage in a coverage angular range and the plurality of subarrays comprising at least two types of subarrays. The at least two types of subarrays comprises: a first type of subarray with a first radiation pattern having at least a first angular region with gain below a first threshold value, and a second type of subarray with a second radiation pattern having at least a second angular region with gain below a second threshold value, wherein the second radiation pattern deviates from the first radiation pattern and the first angular region in the first radiation pattern differs from the second angular region in the second radiation pattern.

TECHNICAL FIELD

The present disclosure relates to the field of active antenna systems,AAS, for controlling coverage in a telecommunication network. Moreparticularly the invention relates to improving the coverage byadjusting the maximal gain envelope pattern for the AAS.

BACKGROUND

In 5G mobile communication systems, advanced antenna system or activeantenna system, AAS, is a key component to improve capacity and coverageby making use of the spatial domain.

An AAS for mobile cellular communication networks is normally requiredto have a broad primary coverage angular range in the horizontal plane,typically φ=±60°, where φ is the azimuthal angle measured from theantenna broadside direction. In the vertical plane, the primary coverageangular range is significantly smaller. The vertical angular range forthe primary coverage depends typically on cell size, height position ofthe AAS, user distribution, and path loss. The primary coverage angularrange is here defined as the angular range where the AAS is to ensurehigh antenna gain and by that high Effective Isotropic Radiated Power,EIRP, and Effective Isotropic Sensitivity, EIS.

Therefore, an AAS 10 typically consists of an array of verticalsub-arrays 11, all identical, as illustrated in FIG. 1, in order tooptimize the array aperture and number of radio chains with respect tothe desired primary coverage angular range. Each subarray 11 comprisesmultiple radiating elements 1 and the subarrays are arranged on anantenna surface 12.

The radiation properties of an AAS of this type can approximately bewritten as

$\begin{matrix}{{{\overset{\rightarrow}{E}\left( {\theta,\varphi} \right)} \approx {{\overset{\rightarrow}{g}\left( {\theta,\varphi} \right)} \cdot {\sum\limits_{n = 1}^{N}{I_{n} \cdot e^{{jk} \cdot r_{n}}}}}} = {{\overset{\rightarrow}{g}\left( {\theta,\varphi} \right)} \cdot {{AF}\left( {\theta,\varphi} \right)}}} & (1)\end{matrix}$whereI_(n)=excitation coefficient of n'th antenna sub-array (beamformingweight){right arrow over (g)}(θ, φ)=antenna radiation pattern of the sub-arraysr_(n)=position of the n'th sub-arrayk=direction vector as a function of θ and φ scaled with 2π/lambdaand

${{AF}\left( {\theta,\varphi} \right)} = {{{Array}{\mspace{11mu}\;}{factor}} = {\sum\limits_{n = 1}^{N}{I_{n} \cdot e^{{jk} \cdot r_{n}}}}}$

That is, for an array of sub-arrays of this type the radiationproperties are proportional to the sub-array pattern times the arrayfactor.

Even though it is within the primary coverage angular range the AAS isto be optimized for high antenna gain, there is also a secondarycoverage angular range where the AAS must have reasonable antenna gainin order to be able to properly serve all user equipment UEs within thecell.

FIG. 2 illustrates a node 20 with an AAS 10, as illustrated in FIG. 1,placed on a mast 15 at a site together with a schematical view of avertical cut of a radiation pattern 22 for the AAS 10, illustrated bysolid lines, as well as a radiation pattern 21 for one subarray 11,illustrated by dashed lines. Dotted lines indicate angular interval inelevation where the subarray pattern low gain region 23 impedes thecoverage of the AAS 10.

To compensate for the path loss the antenna gain should be optimized tothe regions close to the cell border, i.e. a primary coverage angularrange 24, while closer to the site the path loss is significantly less,and the same link budget can be kept with a significantly less antennagain. The latter can be seen as a secondary coverage angular range 25 inthe vertical plane, where a reasonable antenna gain must be ensured.

Consider now equation (1), where the active antenna system has theexcitation coefficients (beamforming weights) I_(n) that in principalcan be selected to optimize the array factor, AF, in any direction, butof course within the limits given by the selected array geometry. Thus,the array factor is not a direct limiting factor to obtain reasonablecoverage in the secondary coverage angular region 25.

However, a limiting factor for the AAS antenna gain in the secondarycoverage angular range will be the antenna radiation pattern 21 of thesub-arrays 11, and particularly if the subarray pattern has more or lessnulls in some direction, a low gain region 23 is present within thesecondary coverage angular range 25. These nulls are set by the hardwaredesign of the sub-array 11 and are therefore independent of the selectedbeamforming weights. Thus, the AAS will not be able to generatereasonable coverage in these directions, defined by the low gain region23, and there will be poor coverage for the UE's there.

Irregular subarrays, sparse arrays, etc. are sometimes considered forapplications such as radar- and communication systems with the purposeto reduce the number of array elements/sub-arrays while maintainingproper main beam coverage and low side lobe levels. In these systemstraffic is confined to angular regions where beams with high gain can bedesigned. In practice this means that the coverage regions fall withinthe main beam of the subarrays. This contrasts with a mobiletelecommunications system where there is also a secondary coverageangular range where the AAS must have reasonable antenna gain in orderto properly serve all UEs within a cell. This means in practice that forthese mobile telecommunications systems the secondary coverage angularrange can fall outside the main beam of the subarray.

SUMMARY

An object of the present disclosure is to provide an active antennasystem which seeks to mitigate, alleviate, or eliminate one or more ofthe above-identified deficiencies in the art and disadvantages singly orin any combination and to provide improved coverage in atelecommunication network.

This object is obtained by an active antenna system, AAS, forcontrolling coverage in a telecommunication network, wherein the AAScomprising a plurality of subarrays each having multiple radiatingelements. The AAS is configured to provide coverage in a coverageangular range and the plurality of subarrays comprising at least twotypes of subarrays. The at least two types of subarrays comprising: afirst type of subarray with a first radiation pattern having at least afirst angular region with gain below a first threshold value, and asecond type of subarray with a second radiation pattern having at leasta second angular region with gain below a second threshold value,wherein the second radiation pattern deviates from the first radiationpattern and the first angular region in the first radiation patterndiffers from the second angular region in the second radiation pattern.

According to an aspect, the first radiation pattern has a gain above thefirst threshold value in the second angular region and/or the secondradiation pattern has a gain above the second threshold value in thefirst angular region.

According to an aspect, subarrays with different radiation patterns maybe created by letting subarrays have: different phase taper and/oramplitude taper and/or different height and/or different elementseparation and/or different number of radiating elements.

This object is also achieved by a method for controlling coverage in atelecommunication network using nodes with an active antenna system,AAS, and the AAS comprises a plurality of subarrays each having multipleradiating elements. The AAS is configured to provide coverage in acoverage angular range and the plurality of subarrays comprising atleast two types of subarrays. The method comprising: configuring a firsttype of subarray with a first radiation pattern having at least a firstangular region with gain below a first threshold value, configuring asecond type of subarray with a second radiation pattern having at leasta second angular region with gain below a second threshold value, andselecting the second radiation pattern to deviate from the firstradiation pattern to ensure that the first angular region in the firstradiation pattern differs from the second angular region in the secondradiation pattern.

This object is also achieved by a node in a telecommunication networkcomprising an active antenna system, AAS, as defined above.

An advantage with the present disclosure is enhanced coverage in asecondary angular coverage range.

Further objects and advantages are disclosed in the detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particulardescription of the example embodiments, as illustrated in theaccompanying drawings in which like reference characters refer to thesame parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe example embodiments.

FIG. 1 illustrates a prior art active antenna system, AAS, with an 8times 4 array consisting of vertical subarrays, each subarray havingthree radiating elements;

FIG. 2 illustrates an AAS placed on a site together with a schematicview of radiation patterns;

FIG. 3 is an example embodiment of an AAS with subarrays havingdifferent electrical down tilt;

FIG. 4 is a first example embodiment of an AAS with subarrays havingdifferent size (height) by having different element separations;

FIGS. 5a and 5b respectively illustrate a second and a third exampleembodiment of an AAS with subarrays having different size (height) byhaving different element separations;

FIG. 6 illustrates an example embodiment of an AAS with subarrays havingdifferent size (height) and number of radiating elements;

FIG. 7 illustrates an example embodiment of an AAS with three types ofsubarrays arranged on an antenna surface;

FIG. 8a illustrates an 8×4 antenna array with the same type ofsubarrays;

FIG. 8b illustrates an 8×4 antenna array with two types of subarrayswith different electrical down tilt;

FIGS. 9a and 9b respectively illustrate maximal vertical gain envelopepattern for the antenna array, and the subarray radiation pattern of thetype of subarray in FIG. 8 a;

FIGS. 10a and 10b respectively illustrate maximal vertical gain envelopepattern for the antenna array, and the subarray radiation patterns ofthe two types of subarrays in FIG. 8 b;

FIGS. 11a and 11b illustrate a beam example for maximal possible gain atspherical angle 151 degrees for the antenna in FIG. 8a and FIG. 8b ,respectively;

FIG. 12a illustrates an 8×2 antenna array with the same type ofsubarrays;

FIG. 12b illustrates an 8×2 antenna array with two types of subarrayswith different number of radiating elements and element separation;

FIGS. 13a and 13b respectively illustrate maximal vertical gain envelopepattern for the antenna array, and the subarray radiation pattern of thetype of subarray in FIG. 12 a;

FIGS. 14a and 14b respectively illustrate maximal vertical gain envelopepattern for the antenna array, and the subarray radiation patterns ofthe two types of subarrays in FIG. 12 b;

FIGS. 14c and 14d respectively illustrate maximal vertical gain envelopepattern for an alternative antenna array, and the subarray radiationpatterns of the two types of subarrays in the alternative antenna array;

FIG. 15 illustrates an 8×2 antenna array with two types of subarrayswith different down tilt;

FIGS. 16a and 16b respectively illustrate maximal vertical gain envelopepattern for the antenna array, and the subarray radiation pattern of thetwo types of subarray in FIG. 15; and

FIG. 17 is a flowchart illustrating embodiments of method steps.

DETAILED DESCRIPTION

Aspects of the present disclosure will be described more fullyhereinafter with reference to the accompanying drawings. The apparatusand method disclosed herein can, however, be realized in many differentforms and should not be construed as being limited to the aspects setforth herein. Like numbers in the drawings refer to like elementsthroughout.

The terminology used herein is for the purpose of describing particularaspects of the disclosure only, and is not intended to limit theinvention. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise.

This disclosure relates to active antenna systems, AAS, consisting of anarray of subarrays and in specific to methods for reducing the impact oflow gain regions, that may include nulls, of subarray pattern on the AASspatial radiation coverage. This objective is achieved by designing someof the subarrays to have different radiation patterns compared to theother subarrays in the AAS in order to avoid that all subarrays have lowgain, e.g. null-depths, in the same direction.

Four principal different embodiments are proposed for an AAS:

Using subarrays with same physical properties, i.e. same size (height)and same number of radiating elements, and configuring some of thesubarrays to have different phase taper (sub-array tilt), and/oramplitude taper. This is exemplified in FIG. 3.

Using subarrays with the same number of radiating elements havingdifferent element separations to obtain subarrays having different size(height). This is exemplified in FIGS. 4, 5 a and 5 b.

Using subarrays with different number of radiating elements to obtainsubarrays having different size (height). This is exemplified in FIG. 6.

Using subarrays with any combination of the above. One example isillustrated in FIG. 7.

FIG. 1 illustrates an active antenna system AAS 10 with an array ofvertical subarrays 11, all identical in order to optimize the arrayaperture and number of radio chains with respect to the desired primarycoverage angular range. Each subarray 11 comprises multiple radiatingelements 1 and the subarrays are arranged on an antenna surface 12.

FIG. 2 illustrates a node 20 with an AAS 10, as illustrated in FIG. 1,placed on a mast 15 at a site together with a schematical view of avertical cut of a radiation pattern 22 for the AAS 10, illustrated bysolid lines, as well as a radiation pattern 21 for one subarray 11,illustrated by dashed lines. Dotted lines indicate angular interval inelevation where the subarray pattern low gain region 23 impedes thecoverage of the AAS 10.

To compensate for the path loss the antenna gain should be optimized tothe regions close to the cell border, i.e. a primary coverage angularrange 24, while closer to the site the path loss is significantly less,and the same link budget can be kept with a significantly less antennagain. The latter can be seen as a secondary coverage angular range 25 inthe vertical plane, where a reasonable antenna gain must be ensured.

Different embodiments will be described in connection to FIGS. 3-7, andillustrative examples will be described in connection to FIGS. 8a-16b .In general, the disclosure relates to an active antenna system, AAS, forcontrolling coverage in a telecommunication network, the AAS comprisinga plurality of subarrays each having multiple radiating elements. TheAAS is configured to provide coverage in a coverage angular range andthe plurality of subarrays comprises at least two types of subarrays.The at least two types of subarrays comprises a first type of subarraywith a first radiation pattern having at least a first angular regionwith gain below a first threshold value, and a second type of subarraywith a second radiation pattern having at least a second angular regionwith gain below a second threshold value, wherein the second radiationpattern deviates from the first radiation pattern and the first angularregion in the first radiation pattern differs from the second angularregion in the second radiation pattern. This also includes the situationwhen identical subarrays are used, and a part of the subarrays aresubject to electrical tilt (e.g. generated remotely) as described inconnection with FIG. 3.

The angular range is in this disclosure expressed in a spherical angle θwith θ=0 in the z direction and 180° in the −z direction (see FIG. 2).The coverage angular range is part of the angular range 0-180 degrees,and may for instance be less than 120 degrees within the angular rangeof 60-180 degrees. The examples are illustrated for elevation angle, butit is possible to implement the same functionality in azimuth.

According to some embodiments, the first angular region overlaps withthe second angular region which will improve the coverage in thesecondary angular coverage range but not eliminate the bad coverage inthe region.

According to some embodiments, the first radiation pattern has a gainabove the first threshold value in the second angular region. Therebyreducing the influence of the low gain region of the second radiationpattern.

According to some embodiments, the second radiation pattern has a gainabove the second threshold value in the first angular region. Therebyeliminating the influence of the low gain region of the first radiationpattern.

According to some embodiments, each angular region is in a directionincluding a null in the respective radiation pattern of the subarrays.

The wording “type of subarray” should not exclude the option whenidentical subarrays are used in the AAS, as long as the different typesof subarray create different radiation pattern during operation. Thismay be achieved by mechanical tilting of the subarray when mounted onthe antenna surface or when wherein the first type of subarray hasdifferent phase taper and/or amplitude taper compared to the second typeof subarray to create different radiation patterns.

Phase taper will create “electrical tilt” of the radiation patterngenerated from a subarray. Amplitude taper (either by itself or incombination with phase taper), will create different radiation patternswith different angular regions where the gain is below a certainthreshold.

According to some embodiments, each threshold value in the respectiveangular region is less than one hundredths, 1/100, of maximal gain ofeach radiation pattern. In some embodiments, each threshold value may beless than one thousands 1/1000 of maximal gain. Each threshold value maybe individually selected and depends on different conditions. Oneexample of such conditions may be service level in the telecommunicationsystem.

According to some embodiments, the first threshold value and the secondthreshold value are identical, or at least substantially identical.

According to some embodiments, a combined radiation pattern created bythe at least two types of subarrays has a maximal gain envelope patternabove a gain threshold value for all angles within the coverage angularrange. The gain threshold value is preferably −30 dB, or higher,relative maximum gain value within the angular coverage range for theenvelope pattern. The gain threshold value may also be expressed as apercentage of maximum gain value for the envelope pattern within theangular range, e.g. if the maximum gain value is 20 dB, the gainthreshold value may be 0.1% of the maximum value, i.e. −10 dB.

When controlling the coverage in a vertical direction (elevation), eachtype of subarray has a height, within which height the multipleradiating elements are arranged. According to some embodiments, thefirst type of subarray has a first height and the second type ofsubarray has a second height, and the first height differs compared tothe second height. According to some embodiments, the first height isthe same as the second height.

Each subarray comprises multiple radiating elements and adjacentlyarranged radiating elements within each subarray have an elementseparation. According to some embodiments, the element separation of thefirst type of subarray differs compared to the element separation of thesecond type of subarray. According to some embodiments, the elementseparation of the first type is equal to the element separation of thesecond type of subarray, but the tilt angle and/or the number ofradiating elements may differ to create subarrays with differentradiation patterns. Element separation may be exemplified as acenter-to-center distance.

According to some embodiments, the first type of subarray comprises afirst number, N, of radiating elements, and the second type of subarraycomprises a second number, M, of radiating elements. According to someembodiments, the first number, N, of radiating elements is equal to thesecond number, M, of radiating elements. According to some embodiments,the first number, N, of radiating elements differs compared to thesecond number, M, of radiating elements.

Any type of suitable radiating elements may be implemented in eachsubarray, and according to some embodiments each radiating element is adual polarized radiating element.

The plurality of subarrays may be arranged over the antenna surface inany suitable way. According to some embodiments, the first type ofsubarray and/or the second type of subarray are non-symmetricallyarranged over the antenna surface in relation to a symmetry line, L.According to some embodiments, the first type of subarray and/or thesecond type of subarray are symmetrically arranged over the antennasurface in relation to a symmetry line, L. This is exemplified in theexample embodiments below.

These aspects will be described in connection to the following figures.

FIG. 3 is an example embodiment of an active antenna system, AAS, 30comprising an 8×4 array antenna with subarrays 11, 31 arranged on anantenna surface 12 and having different down tilt. As mentioned above,the AAS comprises subarrays with same physical properties, i.e. samesize (height) and same number of radiating elements, 1×3. In thisexample two types of subarrays are illustrated: a first type of subarray11 corresponding to the subarray disclosed in connection with FIG. 1 anda second type of subarrays 31 is obtained by configuring some of thesubarrays to have different phase taper (sub-array tilt), and/oramplitude taper compared to the first type of subarray 11. In thisexample the first type of subarrays and the second type of subarrays aresymmetrically arranged over the antenna surface 12 in relation to avertical symmetry line, L.

FIG. 4 is a first example embodiment of an AAS 40 comprising an 8×4array antenna with subarrays 11, 41 arranged on an antenna surface 42and having the same number of radiating elements but different sizes(heights). In this example two types of subarrays are illustrated: afirst type of subarray 11 corresponding to the subarray disclosed inconnection with FIG. 1 and a second type of subarrays 41 with differentsize (height) and thus having different element separation compared tothe first type of subarrays 11. The difference in height between thefirst type of subarray and the second type of subarray is illustrated onthe right side of the AAS. In this example the second type of subarraysare arranged in an upper row 43 of subarrays in the array antenna andthe first type of subarrays are arranged in the lower three rows 44 ofthe array antenna. Furthermore, the first type of subarrays 11 and thesecond type of subarrays 41 are symmetrically arranged over the antennasurface 42 in relation to a vertical symmetry line, L.

FIGS. 5a and 5b respectively illustrate a second and a third exampleembodiment of an AAS with subarrays having different size (height) byhaving different element separations.

The second example of an AAS 50 comprises a 4×4 array antenna withsubarrays 11, 41 arranged on an antenna surface 52 and having the samenumber of radiating elements but different sizes (heights) as describedin connection with FIG. 4. In this example the second type of subarraysare arranged in an upper row 53 a and a lower row 53 b of subarrays inthe array antenna and the first type of subarrays are arranged in themiddle rows 54 of the array antenna. Furthermore, the first type ofsubarrays 11 and the second type of subarrays 41 are symmetricallyarranged over the antenna surface 52 in relation to a vertical symmetryline, L.

The third example of an AAS 55 comprises a 4×4 array antenna withsubarrays 11, 41 arranged on the antenna surface 52 and having the samenumber of radiating elements but different sizes (heights) as describedin connection with FIG. 4. In this example the second type of subarraysare arranged in every second row starting with the upper row 53 a ofsubarrays in the array antenna and the first type of subarrays arearranged in every second row starting with the lower row 53 b of thearray antenna. Furthermore, the first type of subarrays 11 and thesecond type of subarrays 41 are symmetrically arranged over the antennasurface 52 in relation to a vertical symmetry line, L.

FIG. 6 illustrates an example embodiment of an AAS 60 with subarrays 11,61 arranged on an antenna surface 62 and having different size (height)and number of radiating elements. In this example two types of subarraysare illustrated: a first type of subarray 11 corresponding to thesubarray disclosed in connection with FIG. 1 having three radiatingelements, and a second type of subarrays 61 with four radiating elementsand thus different size (height). The element separation for the firsttype of subarray and the second type of subarray is in this example thesame. The difference in height and number of radiating elements betweenthe first type of subarray 11 and the second type of subarray 61 isillustrated on the right side of the AAS 60. In this example the secondtype of subarrays 61 are arranged in an upper row 63 a and a lower row63 b of subarrays in the array antenna and the first type of subarrays11 are arranged in the middle rows 64 of the array antenna. Furthermore,the first type of subarrays 11 and the second type of subarrays 41 aresymmetrically arranged over the antenna surface 52 in relation to avertical symmetry line, L.

FIG. 7 illustrates an example embodiment of an AAS 70 with three typesof subarrays 11, 31, 61 arranged on an antenna surface 72. In thisexample three types of subarrays are illustrated: a first type ofsubarray 11 corresponding to the subarray disclosed in connection withFIG. 1, a second type of subarrays 31 corresponding to the subarraydisclosed in connection with FIG. 3, and a third type of subarrays 61corresponding to the subarray disclosed in connection with figure. Thedifference in height and number of radiating elements of the first typeof subarray 11, the second type of subarray 31, and the third type ofsubarray 61 is illustrated on the right side of the AAS 70. In thisexample the first type of subarrays 11 and the second type of subarrays31 are non-symmetrically arranged in relation to a vertical symmetryline, L, and the third type of subarrays are symmetrically arranged inrelation to the vertical symmetry line, L.

Consider the antenna arrays of sub-arrays in FIGS. 3-6. Assuming theantenna arrays consists of N subarrays in total where one set N1 of thesub-arrays have different sub-array patterns compared to the sub-arraypatterns of the second set N2 of sub-arrays. The radiation properties ofthe array antenna can then be written as:{right arrow over (E)}(θ,φ)≈{right arrow over (g)} ₁(θ,φ)·AF₁(θ,φ)+{right arrow over (g)} ₂(θ,φ)·AF ₂(θ,φ)  (2)where

-   -   {right arrow over (g)}₁(θ, φ)=sub-array antenna radiation        pattern of first set of sub-arrays    -   {right arrow over (g)}₂(θ, φ)=sub-array antenna radiation        pattern of second set of sub-arrays and

${{AF}_{1}\left( {\theta,\varphi} \right)} = {\sum\limits_{m = 1}^{N_{1}}{I_{m} \cdot e^{{jk} \cdot r_{m}}}}$${{AF}_{2}\left( {\theta,\varphi} \right)} = {\sum\limits_{k = {1 + N_{1}}}^{N_{1} + N_{2}}{I_{k} \cdot e^{{jk} \cdot r_{k}}}}$where

-   -   I_(n)=excitation coefficient of n'th antenna sub-array        (beamforming weight)    -   r_(n)=position of the n'th sub-array        N ₁ +N ₂ =N

Equation (1) shows the radiation properties for the case of having oneset of sub-arrays having the same sub-array patterns. The equation showsthat {right arrow over (E)}(θ, φ) will become zero for angles (θ, φ)where the sub-array pattern {right arrow over (g)}(θ, φ) have nullsindependently of the excitation coefficients I_(n).

However, equation (2) shows that as long as {right arrow over (g)}₁(θ,φ) and {right arrow over (g)}₂(θ, φ) do not have sub-array radiationpatterns with nulls in the same direction, the excitation coefficientsI_(n) can for each (θ, φ) always be selected so that there will be nonulls in {right arrow over (E)}(θ, φ).

In more general: Assuming an antenna array consisting of in total Nsubarrays that are divided in P types of sub-arrays having differentsub-array patterns, the radiation properties of the array antenna canthen be written as:

$\begin{matrix}{{\overset{\rightarrow}{E}\left( {\theta,\varphi} \right)} \approx {\sum\limits_{p = 1}^{P}{{{\overset{\rightarrow}{g}}_{p}\left( {\theta,\varphi} \right)} \cdot {{AF}_{p}\left( {\theta,\varphi} \right)}}}} & (3)\end{matrix}$where

-   -   {right arrow over (g)}_(p) (θ, φ)=sub-array antenna radiation        pattern of the P types of sub-arrays and

${{AF}_{p}\left( {\theta,\varphi} \right)} = {\sum\limits_{m = 1}^{N_{p}}{I_{m,p} \cdot e^{{jk} \cdot r_{m,p}}}}$where

-   -   I_(m,p)=excitation coefficient of (m,p)'th antenna sub-array        (beamforming weight)    -   r_(m,p)=position of the (m,p)'th sub-array        N ₁ +N ₂ + . . . +N _(p) =N        In the following, a number of examples will be described.

As a first example, FIG. 8a illustrates an AAS 80 comprising an 8×4antenna array with the same type of subarrays, each subarray 81 having1×2 radiating elements arranged on an antenna surface 82. FIG. 9aillustrates maximal gain envelope pattern 90 in the vertical plane forthe antenna array over an angular range 0°<θ<180°, and FIG. 9billustrates the subarray radiation pattern 91 of one of the subarrays inFIG. 8a . The Maximal gain envelope pattern 90 is the envelope patternobtained when for each (θ, φ) the excitation coefficients I_(n) isselected for maximal gain in the direction (θ, φ). As seen from FIG. 9a, the maximal gain envelope has nulls around 30° and 150°.

For the subarray 81, the radiation pattern 91 have two low gain regions92 and 93, i.e. angular regions with gain below a first threshold value,e.g. −15 dB, within an angular coverage range of 0-180 degrees.

FIG. 8b illustrates an AAS 85 comprising an 8×4 antenna array with twotypes of subarrays 81, 86 with different down tilt, each having 1×2radiating elements. The first type of subarray 81 corresponds to thesubarray described in connection with FIG. 8a with a down tilt and thesecond type of subarray 86 has a different down tilt compared to thefirst type of subarray, as described in connection with FIG. 3.

FIG. 10a shows maximal gain envelope pattern 100 in the vertical planeof the antenna array for the case of having two types of sub-arrays asillustrated in FIG. 8b . In this example there are twenty six subarraysare of the first type 81 with a vertical down tilt of −2.8 degrees, andsix subarrays are of a second type 86 with a vertical down tilt of +12.2degrees and they are symmetrically arranged in relation to a verticalsymmetry line, L. The corresponding subarray patterns are shown in FIG.10b . The radiation pattern 101 of the first type of subarray 81 isillustrated by a solid line, and the radiation pattern 105 of the secondtype of subarray 86 is illustrated by a dashed line. Tilt per subarrayis in this case selected to give zero degree tilt in average over allsubarrays.

For the tilted subarray 81, the radiation pattern 101 have two low gainregions 102 and 103, i.e. angular regions with gain below a firstthreshold value, e.g. −15 dB, within an angular coverage range of 0-180degrees. For the tilted subarray 86, the radiation pattern 105 havethree low gain regions 106, 107 and 108, i.e. angular regions with gainbelow a first threshold value, e.g. −15 dB, within an angular coveragerange of 0-180 degrees. Note that angular regions 102, 103, 106 and 107are non-overlapping, while angular regions 103 and 108 are overlapping.

When comparing FIG. 10a with FIG. 9a , a significant improvement of themax gain envelope around 30° and 150° can be seen with the envelope notexhibiting any nulls.

FIGS. 11a and 11b illustrate a beam example for maximum possible gain atspherical angle 151 degrees for the antenna in FIG. 8a and FIG. 8b ,respectively. The array factor, AF, is in both cases, illustrated inFIG. 11a and FIG. 11b , set to give maximum possible gain at thetaθ=151° The impact of not all subarrays having the same tilt for a narrowbeam generated using the entire array becomes obvious from FIGS. 11a and11b where a beam is designed to have maximum gain at 151 degrees. FIG.11a shows the result where all subarrays are identical, as in FIG. 8a .As the subarrays have a null, or at least very low gain at 151 degrees,the narrow beam 110 generated by the array factor, AF, in combinationwith element patterns will not have any gain in that direction. FIG. 11ashows that the gain for the narrow beam coincide with the maximum gainenvelope pattern around 151 degrees. The narrow beam in FIG. 11a maylook a bit strange as it appears as if the beam actually is pointing atapproximately 0 degrees and not 151 degrees. This is because the beam isformed via four subarrays in elevation and the distance betweensubarrays make a grating lobe appear at 0 degrees when steering the beamtowards an angle of 151 degrees.

FIG. 11b shows that the gain for the narrow beam 111 coincides with theenvelope pattern around 151 degrees and the performance has improvedaround 151 degrees.

As a second example of an example embodiment consider an AAS 120comprising an 8×2 antenna array consisting of 1×4 element sub-arrays 121shown in FIG. 12a . In this case the sub-array height is 2.8λ and theelement separation is 0.7λ (center to center). The total height of theantenna surface of the array antenna is thus 5.6λ.

FIG. 13a illustrates maximal vertical gain envelope pattern 130 of theantenna array for the case of having one type of sub-array 121 accordingto FIG. 12a . FIG. 13b illustrates the subarray radiation pattern 133 ofone of subarrays 121 in FIG. 12a . As seen from FIG. 13a the maximalgain envelope of the antenna array has two nulls below the horizon,θ=90°, at around 115°, as indicated by reference numeral 131, and 145°,as indicated by reference numeral 132.

FIG. 12b illustrates an AAS 125 comprising an 8×2 antenna array with twotypes of subarrays with different number of radiating elements andelement separation. In this example, eight subarrays of a first type 126with a height of 2.64λ consisting of four radiating elements with anelement separation of 0.66λ and eight subarrays of a second type 127with a height of 3.0λ consisting of five radiating elements with anelement separation of 0.60λ. I.e. the total height of the array antennais 5.64λ.

FIG. 14a illustrates maximal vertical gain envelope pattern 140 of theantenna array for the configuration illustrated in FIG. 12b , and thecorresponding sub-array patterns 141 and 142, respectively, are shown inFIG. 14b . The radiation pattern 141 of the first type of subarray 126is illustrated by a solid line, and the radiation pattern 142 of thesecond type of subarray 127 is illustrated by a dashed line.

When comparing FIG. 14a with FIG. 13a it is seen that the nulls belowthe horizon around 115° and 145° are now significantly improved.

If more null-filling is desired this can be accomplished by additionallyincreasing the difference between the subarray patterns. However, thishas to be balanced with the performance of the gain envelope within theprimary coverage angular range.

FIG. 14c illustrates maximal vertical gain envelope pattern 145 of analternative configuration of the antenna array having two types ofsubarrays as described in connection with FIG. 12b . In this examplethere are eight subarrays of a first type with a height of 2.48λconsisting of 4 radiating elements with an element separation of 0.62λand eight subarrays of a second type with a height of 3.10λ consistingof 5 radiating elements with an element separation of 0.62λ. I.e. thetotal height of the array antenna is 5.58λ.

The corresponding sub-array patterns 146 and 147, respectively, areshown in FIG. 14d . The radiation pattern 146 of the first type ofsubarray is illustrated by a solid line, and the radiation pattern 147of the second type of subarray is illustrated by a dashed line.

A third example of an example embodiment also relates to the AAS 120comprising an 8×2 antenna array consisting of 1×4 element sub-arraysshown in FIG. 12a . However, in this example the size of and the numberof radiating elements in the subarrays are kept the same as in FIG. 12a, but there are two types of subarrays with different electrical downtilts.

FIG. 15 illustrates an AAS 150 comprising eight subarrays of a firsttype 151 with 4° electrical down tilt and eight subarrays of a secondtype 152 with 8° electrical down tilt. FIG. 16a shows maximal verticalgain envelope pattern 160 of the antenna array in FIG. 15, and FIG. 16bshows the corresponding sub-array patterns 161 and 162, respectively.The radiation pattern 161 of the first type of subarray 151 isillustrated by a solid line, and the radiation pattern 162 of the secondtype of subarray 152 is illustrated by a dashed line.

When comparing FIG. 16a with FIG. 13a it is seen that the nulls belowthe horizon around 115° and 145° are now significantly improved.

More null-filling can be accomplished by increasing the differencebetween the sub-array down tilts. However, this must be balanced withthe performance of the gain envelope within the primary coverage angularrange.

The present disclosure also relates to a node in a telecommunicationnetwork comprising an active antenna system, AAS, according to anycombination of the example embodiments described in connection withFIGS. 3-16.

FIG. 17 is a flowchart illustrating embodiments of method steps forcontrolling coverage in a telecommunication network using nodes with anactive antenna system, AAS, comprising a plurality of subarrays eachhaving multiple radiating elements. The AAS is configured to providecoverage in a coverage angular range and the plurality of subarrayscomprises at least two types of subarrays. The method comprising:configuring S10 a first type of subarray with a first radiation patternhaving at least a first angular region with gain below a first thresholdvalue, configuring S20 a second type of subarray with a second radiationpattern having at least a second angular region with gain below a secondthreshold value, and selecting S30 the second radiation pattern todeviate from the first radiation pattern to ensure that the firstangular region in the first radiation pattern differs from the secondangular region in the second radiation pattern.

The method may also comprise arranging the subarrays on an antennasurface S40. According to some aspects, the method further comprisesarranging S41 the first type of subarray and/or the second type ofsubarray non-symmetrically over the antenna surface in relation to asymmetry line, L. According to some embodiments, the method furthercomprises arranging S42 the first type of subarray and/or the secondtype of subarray symmetrically over the antenna surface in relation to asymmetry line, L.

According to some embodiments, the method further comprises configuringS11, S21 each angular region to be in a direction including a null inthe respective radiation pattern.

According to some embodiments, the method further comprises selectingS12, S22 each threshold value to be less than one hundredths of maximalgain of each radiation pattern.

According to some embodiments, the first threshold value and the secondthreshold value are selected to be identical, or at least substantiallyidentical.

Each type of subarray has a height, within which height the multipleradiating elements are arranged. According to some embodiments, themethod further comprises configuring S13 the first type of subarray tohave a first height H1 and configuring S23 the second type of subarrayto have a second height H2, and the first height differs compared to thesecond height, H1≠H2.

Adjacently arranged radiating elements within each subarray have anelement separation. According to some embodiments, the method furthercomprises configuring S14, S24 the element separation of the first typeof subarray to differ from the element separation of the second type ofsub array.

According to some embodiments, the method further comprises selectingS15 the first type of subarray to comprise a first number N₁ ofradiating elements, and selecting S25 the second type of subarray tocomprise a second number N₂ of radiating elements. The first number N₁of radiating elements may be equal to the second number N₂ of radiatingelements, or the first number N₁ of radiating elements may differ fromthe second number N₂ of radiating elements.

According to some embodiments, the method further comprises selectingeach radiating element to be a dual polarized radiating element.

According to some embodiments, selecting S30 radiation patterns todeviate further comprising selecting S31 the first radiation pattern tohave a gain above the first threshold value in the second angularregion.

According to some embodiments, selecting S30 radiation patterns todeviate further comprising selecting S32 the second radiation pattern tohave a gain above the second threshold value in the first angularregion.

According to some embodiments, selecting S30 radiation patterns todeviate further comprising selecting S33 the first type of subarray tohave different phase taper and/or amplitude taper compared to the secondtype of subarray to create different radiation patterns.

According to some embodiments, selecting S30 radiation patterns todeviate further comprising selecting S34 the radiation pattern of the atleast two types of subarrays to create a combined radiation pattern withmaximal gain envelope pattern above a gain threshold value for allangles within the coverage angular range.

In some implementations and according to some aspects of the disclosure,the functions or steps noted in the blocks can occur out of the ordernoted in the operational illustrations. For example, two blocks shown insuccession can in fact be executed substantially concurrently or theblocks can sometimes be executed in the reverse order, depending uponthe functionality/acts involved. Also, the functions or steps noted inthe blocks can according to some aspects of the disclosure be executedcontinuously in a loop.

The description of the example embodiments provided herein have beenpresented for purposes of illustration. The description is not intendedto be exhaustive or to limit example embodiments to the precise formdisclosed, and modifications and variations are possible in light of theabove teachings or may be acquired from practice of various alternativesto the provided embodiments. The examples discussed herein were chosenand described in order to explain the principles and the nature ofvarious example embodiments and its practical application to enable oneskilled in the art to utilize the example embodiments in various mannersand with various modifications as are suited to the particular usecontemplated. The features of the embodiments described herein may becombined in all possible combinations of methods, apparatus and systems.It should be appreciated that the example embodiments presented hereinmay be practiced in any combination with each other.

It should be noted that the word “comprising” does not necessarilyexclude the presence of other elements or steps than those listed andthe words “a” or “an” preceding an element do not exclude the presenceof a plurality of such elements. It should further be noted that anyreference signs do not limit the scope of the claims, that the exampleembodiments may be implemented at least in part by means of bothhardware and software, and that several “means”, “units” or “devices”may be represented by the same item of hardware.

In the drawings and specification, there have been disclosed exemplaryaspects of the disclosure. However, many variations and modificationscan be made to these aspects without substantially departing from theprinciples of the present disclosure. Thus, the disclosure should beregarded as illustrative rather than restrictive, and not as beinglimited to the particular aspects discussed above. Accordingly, althoughspecific terms are employed, they are used in a generic and descriptivesense only and not for purposes of limitation.

The invention claimed is:
 1. An active antenna system, AAS, forcontrolling coverage in a telecommunication network, the AAS comprisinga plurality of subarrays each having multiple radiating elements, theAAS being configured to provide coverage in a coverage angular range andthe plurality of subarrays comprising at least two types of subarrays,the at least two types of subarrays comprising: a first type of subarraywith a first radiation pattern having at least a first angular regionwith gain below a first threshold value, and a second type of subarraywith a second radiation pattern having at least a second angular regionwith gain below a second threshold value, wherein the second radiationpattern deviates from the first radiation pattern and the first angularregion in the first radiation pattern differs from the second angularregion in the second radiation pattern.
 2. The active antenna systemaccording to claim 1, wherein the first radiation pattern has a gainabove the first threshold value in the second angular region.
 3. Theactive antenna system according to claim 1, wherein the second radiationpattern has a gain above the second threshold value in the first angularregion.
 4. The active antenna system according to claim 1, wherein thefirst type of subarray has different phase taper and/or amplitude tapercompared to the second type of subarray to create different radiationpatterns.
 5. The active antenna system according to claim 1, whereineach angular region is in a direction including a null in the respectiveradiation pattern.
 6. The active antenna system according to claim 1,wherein each threshold value is less than one hundredths of maximal gainof each radiation pattern.
 7. The active antenna system according toclaim 1, wherein the first threshold value and the second thresholdvalue are identical.
 8. The active antenna system according to claim 1,wherein a combined radiation pattern created by the at least two typesof subarrays has a maximal gain envelope pattern above a gain thresholdvalue for all angles within the coverage angular range.
 9. The activeantenna system according to claim 1, wherein each type of subarray has aheight, within which height the multiple radiating elements arearranged, wherein the first type of subarray having a first height andthe second type of subarray having a second height, and the first heightdiffers compared to the second height.
 10. The active antenna systemaccording to claim 1, wherein adjacently arranged radiating elementswithin each subarray have an element separation, and the elementseparation of the first type of subarray differs compared to the elementseparation of the second type of subarray.
 11. The active antenna systemaccording to claim 1, wherein the first type of subarray comprises afirst number (N₁) of radiating elements, and the second type of subarraycomprises a second number (N₂) of radiating elements.
 12. The activeantenna system according to claim 11, wherein the first number (N₁) ofradiating elements is equal to the second number (N₂) of radiatingelements.
 13. The active antenna system according to claim 11, whereinthe first number (N₁) of radiating elements differs compared to thesecond number (N₂) of radiating elements.
 14. The active antenna systemaccording to claim 1, wherein each radiating element is a dual polarizedradiating element.
 15. The active antenna system according to claim 1,wherein the plurality of subarrays are arranged on an antenna surface,and the first type of subarray and/or the second type of subarray arenon-symmetrically arranged over the antenna surface in relation to asymmetry line (L).
 16. The active antenna system according to claim 1,wherein the plurality of subarrays are arranged on an antenna surface,and the first type of subarray and/or the second type of subarray aresymmetrically arranged over the antenna surface in relation to asymmetry line (L).
 17. A node in a telecommunication network comprisingan active antenna system, AAS, according to claim
 1. 18. A method forcontrolling coverage in a telecommunication network using nodes with anactive antenna system, AAS, the AAS comprising a plurality of subarrayseach having multiple radiating elements, the AAS being configured toprovide coverage in a coverage angular range and the plurality ofsubarrays comprising at least two types of subarrays, the methodcomprising: configuring a first type of subarray with a first radiationpattern having at least a first angular region with gain below a firstthreshold value, configuring a second type of subarray with a secondradiation pattern having at least a second angular region with gainbelow a second threshold value, and selecting the second radiationpattern to deviate from the first radiation pattern to ensure that thefirst angular region in the first radiation pattern differs from thesecond angular region in the second radiation pattern.
 19. The methodfor improving coverage according to claim 18, further comprisingselecting the first radiation pattern to have a gain above the firstthreshold value in the second angular region.
 20. The method forcontrolling coverage according to claim 18, further comprising selectingthe second radiation pattern to have a gain above the second thresholdvalue in the first angular region.
 21. The method for controllingcoverage according to claim 18, further comprising selecting the firsttype of subarray to have different phase taper and/or amplitude tapercompared to the second type of subarray to create different radiationpatterns.
 22. The method for controlling coverage according to claim 18,wherein each angular region is configured to be in a direction includinga null in the respective radiation pattern.
 23. The method forcontrolling coverage according to claim 18, further comprising selectingeach threshold value to be less than one hundredths of maximal gain ofeach radiation pattern.
 24. The method for controlling coverageaccording to claim 18, wherein the first threshold value and the secondthreshold value are selected to be identical.
 25. The method forcontrolling coverage according to claim 18, further comprising selectingthe radiation pattern of the at least two types of subarrays to create acombined radiation pattern with maximal gain envelope pattern above again threshold value for all angles within the coverage angular range.26. The method for controlling coverage according to claim 18, whereineach type of subarray has a height, within which height the multipleradiating elements are arranged, and wherein the method furthercomprises configuring the first type of subarray to have a first heightand configuring the second type of subarray to have a second height, andthe first height differs compared to the second height.
 27. The methodfor controlling coverage according to claim 18, wherein adjacentlyarranged radiating elements within each subarray have an elementseparation, and wherein the method further comprises configuring theelement separation of the first type of subarray to differ from theelement separation of the second type of subarray.
 28. The method forcontrolling coverage according to claim 18, further comprisingconfiguring the first type of subarray to comprise a first number (N₁)of radiating elements, and configuring the second type of subarray tocomprise a second number (N₂) of radiating elements.
 29. The method forcontrolling coverage according to claim 28, further comprising selectingthe first number (N₁) of radiating elements to be equal to the secondnumber (N₂) of radiating elements.
 30. The method for controllingcoverage according to claim 28, further comprising selecting the firstnumber (N₁) of radiating elements to differ from the second number (N₂)of radiating elements.
 31. The method for controlling coverage accordingto claim 18, further comprising selecting each radiating element to be adual polarized radiating element.
 32. The method for controllingcoverage according to claim 18, wherein the plurality of subarrays arearranged on an antenna surface, and the method further comprisesarranging the first type of subarray and/or the second type of subarraynon-symmetrically over the antenna surface in relation to a symmetryline (L).
 33. The method for controlling coverage according to claim 18,wherein the plurality of subarrays are arranged on an antenna surface,and the method further comprises arranging the first type of subarrayand/or the second type of subarray symmetrically over the antennasurface in relation to a symmetry line (L).